Priority is claimed to Japanese Patent Application Number JP2003-333888 filed on Sep. 25, 2003, the disclosure of which is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates to a hybrid integrated circuit device and a method of manufacturing the same. The present invention particularly relates to a hybrid integrated circuit device obtained by manufacturing multiple circuit boards from one large metal board, and a method of manufacturing the hybrid integrated circuit device.
2. Description of the Related Art
A description will be given of a constitution of a conventional hybrid integrated circuit device with reference to FIGS. 11A and 11B. FIG. 11A is a perspective view of a hybrid integrated circuit device 6, and FIG. 11B is a sectional view taken along the line X–X′ in FIG. 11A.
Referring to FIGS. 11A and 11B, the conventional hybrid integrated circuit device 6 has a constitution as follows. The hybrid integrated circuit device 6 includes: a rectangular board 60; conductive patterns 62 formed on an insulating layer 61 provided on the surface of the board 60; circuit elements 63 bonded to the conductive patterns 62; fine metal wires 65 electrically connecting the circuit elements 63 to the conductive patterns 62; and leads 64 electrically connected to the conductive patterns 62. A hybrid integrated circuit formed on the surface of the circuit board 60 is sealed with insulation resin, a case material, or the like, whereby the hybrid integrated circuit device 6 is completed as a product.
Next, a description will be given of a method of manufacturing the hybrid integrated circuit device 6 with reference to FIGS. 12A to 14.
A description will be given of a process of splitting a large metal board 66A into strips with reference to FIGS. 12A and 12B. Of these drawings, FIG. 12A is a plan view of the large metal board 66A, and FIG. 12B is a sectional view of the large metal board 66A.
Referring to FIG. 12A, a method of splitting the large metal board 66A into strips will be described. Here, the large metal board 66A is split into the strips along dicing lines 4D. This splitting is performed by shearing using shearing force. Out of consideration for workability in a later bonding process or the like, a split-off metal board (strip) may be further divided into two or more pieces. Here, each split-off metal board (strip) is divided into two metal boards 66B with different lengths.
Referring to FIG. 12B, a constitution of the metal board 66A will be described. Here, the board 66A is a board made of aluminum, and both faces thereof have been anodized. Moreover, the surface where hybrid integrated circuits will be formed is provided with the insulating layer 61 in order to insulate the metal board 66A from conductive patterns. Furthermore, copper foil 68, which becomes the conductive patterns 62, is pressed onto the insulating layer 61.
A description will be given of a process of forming hybrid integrated circuits 67 on the surface of the metal board 66B, which is a split-off narrow board, with reference to FIGS. 13A and 13B. Of these drawings, FIG. 13A is a plan view of the narrow metal board 66B on which a plurality of the hybrid integrated circuits 67 are formed, and FIG. 13B is a sectional view of FIG. 13A.
First, the conductive patterns 62 are formed by etching the copper foil 68 pressed onto the insulating layer 61. Here, the copper foil 68 is etched into the conductive patterns 62 so that a plurality of the hybrid integrated circuits are formed on the narrow metal board 66B. Moreover, in some cases, a resin overcoating is applied onto the conductive patterns 62 for the purpose of protecting the conductive patterns 62.
Next, the circuit elements 63 are bonded onto the conductive patterns 62 at respective predetermined positions using a brazing material such as soft solder. For the circuit elements 63, passive elements and active elements can be employed in general. In addition, when power elements are mounted, the elements are mounted on heat sinks bonded onto the conductive patterns.
A description will be given of a method of splitting the metal board 66B with the plurality of hybrid integrated circuits 67 formed thereon into the individual circuit boards 60, with reference to FIG. 14. Each of the circuit boards 60, on the surfaces of which the hybrid integrated circuits 67 are respectively formed, is split off from the metal board 66B by punching out the portion of the circuit board 60 using a press. Here, the press punches the metal board 66B out from the side where the hybrid integrated circuits 67 are formed. Therefore, margins, where the conductive patterns 62 and the circuit elements 63 are not formed, are provided in the peripheral end portions of the circuit boards 60.
The circuit boards 60, individually separated in the above-described process, are completed as products after subjected to a process of sealing the hybrid integrated circuits 67 and the like.
However, the above-described hybrid integrated circuit device and method of manufacturing the same have had problems as described below.
Since the circuit boards 60 are separated from the metal board 66B by pressing the metal board 66B, portions at least within 2 mm from the peripheral end portions of the circuit boards 60 serve as margins. Accordingly, the peripheral portions of the circuit boards 60 are dead spaces, and therefore, there has been a problem that an entire device becomes large even if the degree of integration of the hybrid integrated circuit 67 is increased.
For a similar reason to the foregoing, some circuit elements 63 such as heat sinks cannot be placed in the peripheral portions of the circuit boards. This fact becomes a constraint when the conductive patterns 62 are designed, and therefore, there has been a problem that the density of the hybrid integrated circuit cannot be increased.
Moreover, since the side surface portions of the board are vertically formed, there has been a problem that when the board is sealed with resin, the adhesion between the board and the sealing resin is poor.
When the circuit board 60 is separated from the metal board 66B by “punching” using a press, there has been a problem that cracks occur in the insulating layer 61, formed on the surface of the circuit board 60, due to an impact of the “punching.”
In the case in particular where multi-layer interconnections are formed on the surface of the circuit board 60, the insulating layers become thick depending on the number of layers to be stacked. Accordingly, when multi-layer interconnections are formed, the problem of the occurrence of cracks in the insulating layers 61 has arisen more noticeably.
The insulating layer 61 is formed on the surface of the metal board 66B. The insulating layer 61 is very hard because it is highly filled with alumina. Accordingly, there has been a problem that a blade of a press for performing “punching” is worn out soon. Moreover, the replacement of a blade of a press is work requiring skilled labor, and what is more, takes a very long time. Therefore, there has been a problem that the productivity is reduced. In addition, this blade used for punching is very expensive. Therefore, further, the fact that the life of this blade is very short may cause an increase in the cost of an entire device.
When the circuit board 60 is separated from the metal board 66B by “punching” using a press, the peripheral portions of the metal board 66B become a loss of material. Accordingly, there has been a problem that the loss from disposal of the metal board 66B, which is a material, becomes large.